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fider the immenfe (Irengtli which is obtained by the arrange- 

 ment of the mufciilar fibres in the gizzard, and the horny 

 conliftence of its inner coat, there appears notliing incredible 

 in thefe tfFefts. And there is Hill another circnmllance, not 

 before mentioned, which fully accounts for fuch extraordi- 

 nary powers of trituration : every mufcnlar llomach or giz- 

 zard contains a number of fmall ftones or pebbles ; the ii/e 

 of the ftones is proportioned to that of the bird. Their 

 number is fubjeft to vary from many accidental caufes. Two 

 hundred have been reckoned in a lurkey-hen, and above a 

 thoufand have been taken from the gizzard oi one goofe. 



Spallan-.'.ani denied that thefe Hones were at all required 

 for the comminution of the food. He has endeavoured to 

 fupport his opinion by feveral experiments, which are, how- 

 ever, not clear or conlifUnt with each other, and in contra- 

 di<5tion to general obfervation ; for it is well known, that 

 bird'i do not thrive when they cannot obtain fmall ftones, 

 and that it is part of the duty of the parent to provide them 

 for their young, before they leave the nell. Spallanzani 

 acknowledges that he could not procure any bird io young, 

 that it had not fome ftones in its gizzard ; and therefore he 

 was obliged to rear pigeons and turkeys even from the (hell, 

 before ke was able to fucceed. Birds, fo tar from fwallow- 

 ing ftones from kcennefs of appetite, or in raiftake for food, 

 feek out and feleft tliofe moll fuitable to their purpofc, 

 which are almoft all bits of quartz, of an equal fize, and a 

 roundifti fitjure, with many fmall (liarp angles. 



JLarge birds, as the Jlrulh'ious kind, the buJlariJ, Sec. are 

 in the habit of fwallowing coins and pitces of metal, which 

 neceftarily fuffcra redudion by the friftion to which they are 

 CKpofed ; and hence has arilen the ridiculous notion of the 

 o/irirh digetting iron. 



We have no helitation in deciding, that the extraneous 

 bodies found in the gizzard are abiolutcly required for the 

 perfeft divifion of the food ufed by thofe birds that employ 

 them. In further proof of which opinion it may be men- 

 tioned, that they are proportioned in quantity to the degree 

 of mnfcularity pofrefted by the ventricle, and tlie nutritive 

 quality of the food ; and lh:!t thofe birds which have thin 

 ilomachs, and hve upon animal food, never dcfigncdly fwal- 

 low ftones, or othsr indigeftible fubftancej. 



In order to afcertain the mode of operation of the giz- 

 zard in the living body, Reaumur opened feveral fowls 

 during the proccfs of digeftion. One iiiftance atone fhewed 

 any motion in the part, which confifted in alternate con- 

 tnftions and dilatations, fl wly and gradually performed. 

 Spallanzani iuftituted Ijmilar experiments upon feveral birds, 

 with no better fuccels, beivg feldo n able to dcteft the Icaft 

 motion ; and when he did perceive any, it was irregular, 

 partial, a'd in''.iftindi. Tnis he attributed to the violence 

 committed by opening the animal's body, which no doubt 

 caufes the motions to be lefs ftrong and regular ; but the 

 gizzard's exhibiting ext."rnally fo little aftion, depends upon 

 the difpofition of the fibres. in the interior of ^he digaitric 

 mufcle, which are calculated, not for performing extenfive 

 motions, but for exerting an immenfe concentrated force 

 upon whatever may come witliin their influence. 



The moft fatisfa(Sory, as well as convenient mode of ex- 

 amini::g the aflions of the living gizzard is, to provide a 

 Very lean, voting birl, which has thin parietes to the ab- 

 domen. The lide of the belly being deprived of feathers, 

 all the motions of the gizzard can be both felt and feen. 

 We have thus afcertained them, to conCll in alternate con- 

 traftions of the di^aftric mufcle, and ot the intermediate 

 parts of the ventricle. When the mufcle afts, its figure is 

 not perceptibly changed, but it feels as hard as a ftone : 

 wpou its relaxation, the parietes of the ventricle urge their 



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contents again between the two grinding furfaces, when the 

 mufcle repeats its powerful contraftion, by which the fub- 

 ftances interpofed are fubmitted to a preffure hkc that of a 

 vice, accompanied by a flight rolling motion of tlie furfaces 

 upon each other. Thefe alternate attions fucceed each 

 other very flowly, but with regularity. 



When the food and ftones roll under the pretTMre of the 

 digaftric mufcle, a found is heard exaftly like what is pro- 

 duted by the tide coming upon a ftiore, whcic there are 

 many loofe ftones. This occurs w-ith the fume intervals of 

 time, alfo, which are obferved between the flux and reflux 

 of the tide ; and if the ear be applied to the body of the 

 bird, during the time that the gizzard is in adiion, the 

 found of the ebbing and flowing of the tide is imitated fo 

 perfeftly in loudnefs, and every other refpeft, that it is 

 difficult to conceive it is occafioned by any other caufe. 



During the time that the food is undergoing a very mi- 

 nute divifion, in the manner defcribed, the gaftric juice is 

 diftilled from the bulbus glandulofus in greater quantity 

 than ufual, and a more intimate mixture is formed of the 

 digeftive fluid and the triturated food, than could be accom- 

 pliflied under any other circumftances ; and therefore we 

 may look upon the procefs of digeftion in graminivorous 

 birds, as not only more complicated, but more pcrfecl than 

 it is in animals in general. 



Intejl'mes, 



Thefe are divided in birds, as in other animals, into 

 great and fmall, although the terms are not very appro- 

 priate ; there not being in general any material difference in 

 the magnitude of each. 



Theyi;;^?// 'intejl'mes exceed the large very much in length ; 

 they are fituated chiefly in the anterior and right fide of the 

 abdomen, where they are ftriftly confined by the proccfTes 

 of peritoneum, Vv-hich form the air-cells. The convolutions 

 of the inteftines are very regular, and confift in fucccflive 

 doublings one fliorter than another, which give the appear- 

 ance, on opening the abdomen, of a coil ot rope, particu- 

 larly in thofe birds which have the fmall inteftines of confi- 

 derable length. This cfl'cft depends upon the figure of the 

 mefcntery, which is not compoled in quite the fame manner 

 as in mammalia. 



The diftinftion of the fmall inteftines into duodenum, je- 

 junum, and ilium, is at all times to a certain degree arbi- 

 trary, and is ftill lefs allowable in birds. The only portion 

 which deferves to be diftinguiflied from the reft nf the tube, 

 is the firft coil ; which afcends on the right fide of the fto- 

 mach, including in its refleftion the pancreas, and receives 

 the biliary and pancreatic dufts. 



The length of the inteftines is determined ufually accord- 

 ing to the nature of the food upon which the bird lives ; they 

 are tongeft in the graminivorous, and very fhort in the acci- 

 p'llns. Many birds, however, which ufe a mixed rood, or 

 even live altogether upon fifh, have the fmall inteftines of 

 great length ; this is the cafe with the heron, and feveral 

 others. The whole of the inteftines of the cormorant, ac- 

 cording to the Parifian anatomills, mcafured feven feet long ; 

 and wtiat is difficult to explain, thofe of the lii/hird?i\\A. caf- 

 fo-Mary, although large and graminivorous birds, were only 

 tour feet in length. The different cjlr'iches diflTefted by the 

 Academy, varied materially with refpeft to the length of the 

 inteftinal canal, one fubjeft meafuring fifty feet, another for- 

 ty-two, a third thirty-three, and a fourth twenty-nine feet. 



There is very little peculiar to be noticed in the ftrufture 

 of the fmall inteftines. They are, as in other animals, co- 

 vered externally by peritoneum, have two layers of mulcular 

 fibres, and their internal furface is furnifhed with thofe innu- 

 merable line YEifcular proceles called v'lU'u The graminivo- 

 rous 



